TWI386681B - Method and device for manipulating color in a display - Google Patents

Description

Method and apparatus for manipulating colors in a display

The technical field of the invention relates to microelectromechanical systems (MEMS).

Microelectromechanical systems (MEMS) include micromechanical components, flip-flops, and electronics. The micromechanical component can be fabricated by deposition, etching, or other micromachining process that etches away portions of the substrate and/or deposited material layer or can add multiple layers to form electrical and electromechanical devices. One type of MEMS device is referred to as an interferometric modulator. The interferometric modulator can include a pair of conductive plates, one or both of which can be fully or partially transparent and/or reflective, and capable of making relative motion when an appropriate electrical signal is applied. One of the plates may comprise a stationary layer deposited on a substrate, and the other plate may comprise a metal film separating the stationary layer by an air gap. The above described devices have a wide range of applications, and it would be beneficial in the art to utilize and/or modify the characteristics of such devices, such that their characteristics can be used to retrofit existing products and to manufacture new products that are not yet developed.

The systems, methods, and devices of the present invention each have a plurality of aspects, and any single aspect cannot individually determine its desired properties. A more general description of its features will now be provided, and this does not limit the scope of the invention. In considering this discussion, and particularly after reading the section entitled "Implementation," it will be appreciated that the features of the present invention provide advantages over other display devices.

An embodiment is a display device. The device includes a plurality of interferometric modulators. The plurality of interferometric modulators includes at least one interferometric modulator configured to output red light, at least one interferometric modulator configured to output green light, and at least one configured to output blue light Interferometric modulator. The red light, the green light, and the blue light are mixed to produce the white light having an output of a normalized white point.

An embodiment is a display device. The apparatus includes at least one display element including a reflective surface configured to be positioned at a distance from a portion of the reflective surface. The at least one display element is selected to produce white light characterized by a normalized white point.

Another embodiment is a display device. The apparatus includes a plurality of display elements, each display element including a reflective surface configured to be positioned at a distance from a partially reflective surface. The plurality of display elements are configured to output white light characterized by a normalized white point.

Another embodiment is a method of making a display. The method includes forming at least one display element configured to output light. Forming the display element includes forming a portion of the reflective surface and a reflective surface configured to be positioned at a distance from the partially reflective surface. The at least one display element is formed such that white light produced by the at least one display element is characterized by a normalized white point.

Another embodiment is a method of making a display. The method includes forming a plurality of display elements configured to output light. Each of the plurality of display elements includes a reflective surface configured to be positioned at a distance from the partially reflective surface. The display element is formed such that white light produced by the plurality of display elements is characterized by a normalized white point.

Another embodiment is a display device. The device includes a first member for selectively reflecting light having a first color. The apparatus further includes a second member for selectively reflecting light having a second color. The apparatus further includes a third member for selectively reflecting light having a third color. The light reflected by the first, second, and third members is mixed to produce white light characterized by a normalized white point.

Another embodiment is a display device. The device includes means for reflecting light and means for partially reflecting light. The member for reflecting light and the member for partially reflecting light include members for modulating light. The light modulation member is configured to interferometrically generate white light characterized by a standardized white point.

Another embodiment is a display device. The device includes means for reflecting light and means for partially reflecting light. The member for reflecting light and the member for partially reflecting light include members for display. The display member is configured to output white light characterized by a standardized white point.

Various embodiments include a display that includes an interferometric display element that is formed to produce white light having selected spectral properties. An embodiment includes a display that produces white light by using an interferometric modulator configured to reflect cyan and yellow light. Another embodiment includes a display that produces white light by using an interferometric modulator that reflects green light, the interferometric modulator that reflects green light by a filter that selectively transmits magenta light. Embodiments also include a display that reflects white light characterized by a standardized white point. The white point of such a display may be different from the white point of the light that illuminates the display.

The following detailed description is directed to certain specific embodiments of the invention. However, the invention can be implemented in a multitude of different ways. In this description, reference will be made to the drawings As will be readily apparent from the description below, the present invention can be implemented in any device configured to display an image whether the image is dynamic (eg, video) or static (eg, still image) and is textual. Or a picture. More specifically, it is contemplated that the present invention can be implemented in or associated with a variety of electronic devices such as, but not limited to, mobile phones, wireless devices, personal digital assistants (PDAs), palmtop computers, or portable Computers, GPS receivers/navivers, cameras, MP3 players, cameras, game consoles, watches, clocks, calculators, TV monitors, flat panel displays, computer monitors, car displays (eg, odometer displays, etc.), Cockpit controller and/or display, camera view display (eg, rear view camera display of the vehicle), electronic photo, electronic signage or signage, projector, architectural structure, packaging and aesthetic structure (eg, an image of a piece of jewelry) monitor). MEMS devices having structures similar to those described herein can also be used in non-display applications such as electronic switching devices.

Figure 1 illustrates an embodiment of an interferometric modulator display incorporating an interferometric MEMS display element. In such devices, the pixels are in a bright or dark state. In the bright ("on" or "on" state), the display element reflects a significant portion of the incident visible light to the user. When in a dark ("off" or "off" state), the display element has little incident visible light reflected to the user. Depending on the embodiment, the light reflecting properties of the "on" and "off" states can be reversed. MEMS pixels can be configured to primarily reflect selected colors, allowing for color display outside of black and white display.

1 is an isometric view depicting two adjacent pixels in a series of pixels of a visual display, each of which includes a MEMS interferometric modulator. In some embodiments, an interferometric modulator display includes a column/row array of the interferometric modulators. Each interferometric modulator includes a pair of reflective layers positioned at a variable and controllable distance from one another to form an optical resonant cavity having at least one variable dimension. In an embodiment, one of the reflective layers is moveable between two positions. In the first position (referred to herein as the released state), the movable layer is positioned a relatively large distance from the partially fixed reflective layer. In the second position, the movable layer is positioned closer to the partially reflective layer. The incident light reflected from the two layers undergoes constructive or destructive interference according to the position of the movable reflective layer, thereby producing a total reflection or non-reflection state for each pixel.

The depicted portion of the pixel array of Figure 1 includes two adjacent interferometric modulators 12a and 12b. In the interferometric modulator 12a on the left side, the movable height reflective layer 14a is illustrated in a release position at a predetermined distance from the fixed partial reflection layer 16a. In the interferometric modulator 12b on the right side, the movable height reflective layer 14b is illustrated in a triggering position near the fixed partial reflective layer 16b.

The pinned layers 16a, 16b are electrically conductive, partially transparent, and partially reflective, and can be fabricated, for example, by depositing one or more layers of chromium and indium tin oxide on the transparent substrate 20. The layers are patterned into parallel strips and may form column electrodes in a display device as further described below. The movable layers 14a, 14b can be formed as a series of parallel strips of one of the intervening sacrificial materials deposited on top of the pillars 18 or a plurality of deposited metal layers (perpendicular to the column electrodes 16a, 16b) and deposited between the pillars 18. When the sacrificial material is etched away, the deformable metal layer is separated from the fixed metal layer by a defined air gap 19. A highly conductive and reflective material, such as aluminum, can be used as the deformable layer, and the parallel strips can form row electrodes in a display device.

Without voltage applied, cavity 19 remains between layers 14a, 16a and the deformable layer is in a mechanically relaxed state, as illustrated by pixel 12a in FIG. However, when a potential difference is applied to a selected column and row, the capacitance formed at the intersection of the column electrode and the row electrode of the corresponding pixel will be charged, and the electrostatic force pulls the electrodes together. If the voltage is sufficiently high, as illustrated by the pixel 12b on the right side of Figure 1, the movable layer is deformed and is pressed against the fixed layer (a dielectric material not shown in this figure can be deposited on the fixed layer to prevent short circuit And control the separation distance). The operating state is the same regardless of the polarity of the applied potential difference. In this way, the column/row trigger that can control the state of the reflective-non-reflective pixel is similar in many methods to conventional LCD and other display technologies.

2 through 5B illustrate an exemplary process and system for using an interferometric modulator array in a display application. 2 is a system block diagram illustrating one embodiment of an electronic device that can include aspects of the present invention. In the exemplary embodiment, the electronic device includes a processor 21, which can be any general purpose single or multi-chip microprocessor, such as ARM, Pentium. Pentium II Pentium III , Pentium IV Pentium Pro, 8051, MIPS Power PC ALPHA Or any dedicated microprocessor, such as a digital signal processor, a microcontroller, or a programmable gate array. As is known in the art, processor 21 can be configured to execute one or more software modules. In addition to executing an operating system, the processor can be configured to execute one or more software applications, including a web browser, a phone application, an email program, or any other software application.

In an embodiment, processor 21 may also be configured to communicate with an array controller 22. In one embodiment, array controller 22 includes a column driver circuit 24 and a row driver circuit 26 that provide signals to pixel array 30. A cross-sectional view of the array illustrated in Figure 1 is illustrated by line 1-1 in Figure 2 . For MEMS interferometric modulators, the column/row triggering protocol can utilize the hysteresis properties of the devices illustrated in Figure 3. It may require, for example, a potential difference of 10 volts to deform the movable layer from a released state to a triggered state. However, as the voltage decreases from this value, the movable layer maintains its state as the voltage drops back below 10 volts. In the exemplary embodiment of Figure 3, the movable layer does not completely release ' until the voltage drops below 2 volts. There is thus a range of voltages, in the example shown in Figure 3, of about 3 volts to 7 volts, in which there is a window of applied voltage within which the device is stabilized in a released or triggered state. This is referred to herein as a "hysteresis window" or "stability window." For a display array having the hysteresis nature of Figure 3, the column/row triggering protocol can be designed to expose the pixel to be triggered in the gating column to a voltage difference of about 10 volts during column gating, and to be released The pixels are exposed to a voltage difference close to 0 volts. After gating, the pixel is exposed to a steady-state voltage difference of about 5 volts to maintain it in any state in which the column is gated. After being written, in this example, each pixel experiences a potential difference within a 3-7 volt "stability window." This feature allows the pixel design illustrated in Figure 1 to be stabilized in an existing triggered or released state under the same applied voltage conditions. Since each pixel of the interferometric modulator is substantially a capacitor formed by a fixed layer and a moving reflective layer, whether in a triggered state or a released state, the steady state can be maintained at a voltage within a hysteresis window with almost no Power consumption. If the applied potential is fixed, substantially no current flows into the pixel.

In a typical application, a display frame can be formed by determining a set of row electrodes based on the trigger pixels to be grouped in the first column. Thereafter, a column pulse is applied to the electrodes of column 1, thereby triggering pixels corresponding to the determined row lines. Thereafter, the row electrodes of the determined group are changed to correspond to the trigger pixels to be grouped in the second column. Thereafter, a pulse is applied to the electrodes of column 2 to trigger the appropriate pixels in column 2 in accordance with the determined row electrodes. The pixels of column 1 are unaffected by the pulse of column 2 and remain in their set state during the pulse of column 1. This process can be repeated for the entire series in a sequential manner to form the frame. Typically, the frames are refreshed and/or updated by new display data by continuously repeating the process at a desired number of frames per second. A wide variety of protocols for driving columns and row electrodes of pixel arrays to produce display frames are also well known, and such protocols can be used in conjunction with the present invention.

4, 5A and 5B illustrate possible triggering protocols for forming one of the display frames on the 3x3 array of FIG. 4 illustrates a set of possible row and column voltage levels that can be used to represent the pixels of the hysteresis curve of FIG. In the embodiment of FIG. 4, the trigger a pixel involves setting the appropriate row to -V _bias, and the appropriate column to + △ V, may correspond to -5 volts and +5 volts. With the appropriate row to + V _bias and setting the appropriate column to the same + △ V, producing a zero volt potential difference across the pixel of the pixel of release is achieved. In their column voltage is maintained at zero volts column, the pixels are stable in whatever state they were originally in, the row and in the + V _bias -V _bias independent Or.

Figure 5B is a timing diagram showing a series of columns and rows of signals applied to the 3 x 3 array shown in Figure 2, which will result in the arrangement of the display illustrated in Figure 5A, wherein the pixels that are triggered are non-reflective. Prior to writing the frame illustrated in Figure 5A, the pixels can be in any state, and in this example, all columns are at 0 volts and all rows are at +5 volts. By applying the voltages, all pixels are stabilized in their existing trigger or release state.

In the frame shown in Fig. 5A, pixels (1, 1), (1, 2), (2, 2), (3, 2), and (3, 3) are triggered. To achieve this, during column 1 "linetime", row 1 and row 2 are set to -5 volts and row 3 is set to +5 volts. This does not change the state of any pixels because all pixels remain in a stable window of 3-7 volts. Thereafter, column 1 is strobed by a pulse that rises from 0 volts to 5 volts and then back to 0 volts. This triggers the pixels (1, 1) and (1, 2) and releases the pixels (1, 3). All other pixels in the array are unaffected. To set column 2 to the desired state, set row 2 to -5 volts and set row 1 and row 3 to +5 volts. Thereafter, the same strobe applied to column 2 will trigger pixel (2, 2) and release pixels (2, 1) and (2, 3). Again, the other pixels in the array are unaffected. Similarly, column 3 is set by setting row 2 and row 3 to -5 volts and row 1 to +5 volts. The strobe pulse of column 3 sets the column 3 pixels as shown in Figure 5A. After writing the frame, the column potential is zero and the row potential can be maintained at +5 or -5 volts, and thereafter the display will stabilize at the arrangement shown in Figure 5A. It should be understood that the same procedure can be applied to an array of tens or hundreds of columns and rows. It should also be appreciated that the timing, order, and level of voltages used to perform column triggering and row triggering can vary widely within the general principles described above, and that the above examples are merely illustrative and that any trigger voltage method can be used with the present invention. use together.

The detailed structure of the interferometric modulator operating according to the above principles can vary widely. For example, Figures 6A-6C illustrate three different embodiments of a moving mirror structure. Figure 6A is a cross-sectional view of the embodiment of Figure 1 with a strip of metal material 14 deposited on the orthogonally extending support members 18. In FIG. 6B, the movable reflective material 14 is attached only to the corners of the support, on the tether 32. In FIG. 6C, the movable reflective material 14 is suspended from the deformable layer 34. This embodiment has advantages because the structural design of the reflective material 14 and the materials used can be optimized in terms of optical properties, and the structural design of the deformable layer 34 and the materials used can be optimized in terms of desired mechanical properties. Further, a dielectric material layer 104 is formed on the fixed layer. The production of various types of interferometric devices is described in a number of publications, including, for example, U.S. Patent Application Serial No. 2004/0051, 929. A wide variety of well known techniques can be used to produce the structures described above that contain a series of material deposition, patterning, and etching steps.

As discussed above with reference to Figure 1, modulator 12 (i.e., both modulators 12a and 12b) includes a mirror 14 (i.e., mirrors 14a and 14b) and mirrors 16 (mirrors 16a and 16b, respectively). The light cavity between. The characteristic distance of the optical cavity or the effective optical path length d determines the resonant wavelength λ of the optical cavity, thereby determining the resonant wavelength λ of the interferometric modulator 12. One of the peak resonance visible wavelengths λ of the interferometric modulator 12 generally corresponds to the perceived color of the light reflected by the modulator 12. Mathematically, the optical path length d is equal to Nλ, where N is an integer. Thus a given resonant wavelength λ via the optical path length d is The interferometric modulator 12 such as λ (N = 1), λ (N = 2), and 3/2 λ (N = 3) reflects. The integer N can be referred to as the interference level of the reflected light. As used herein, the level of modulator 12 also refers to the level N of light reflected by modulator 12 when mirror 14 is at at least one location. For example, a first stage red interferometric modulator 12 can have a large optical path length d of about 325 nm, corresponding to a wavelength λ of about 650 nm. Thus, a second stage red interferometric modulator 12 can have an optical path length d of approximately 650 nm. Typically, the modulator 12 having a higher level reflects light over a narrower range of wavelengths, for example, having a higher "Q" value, resulting in a more saturated color. The saturation of the modulator 12, which contains a color pixel, affects the nature of the display, such as the color gamut and white point of the display. For example, in order for a display using the second stage modulator 12 to have the same white point or color balance as a display comprising a first level modulator that reflects light of the same general color effect, The secondary modulator 12 can be selected to have a different center peak light wavelength.

It is noted that in a particular embodiment such as that illustrated in FIG. 1, the optical path length d is substantially equal to the distance between mirrors 14 and 16. Wherein the space between mirrors 14 and 16 contains only one gas having a refractive index close to 1, such as air, the effective optical path length is substantially equal to the distance between mirrors 14 and 16. Other embodiments, such as illustrated in Figure 6C, include a layer of dielectric material 104. The refractive index of such dielectric materials is typically greater than one. In such embodiments, the optical cavity is formed to have the desired optical path by selecting the distance between the mirrors 14 and 16 and the thickness and refractive index of the dielectric layer 104 or any other layer between the mirrors 14 and 16. Length d. For example, in the embodiment illustrated in Figure 6c, the optical cavity includes a dielectric layer 104 other than the air gap, the optical path length d being equal to d ₁ n ₁ + d ₂ n ₂ , where d ₁ is the thickness of layer 1 n ₁ is the refractive index of layer 1; similarly, d ₂ is the thickness of layer 2 and n ₂ is the refractive index of layer 2.

Generally, when the modulator 12 is viewed from a different angle, the color of the light reflected by the interferometric modulator 12 varies. FIG. 7 is a side cross-sectional view of the interferometric modulator 12 illustrating the optical path through the modulator 12. The color of the light reflected from the interferometric modulator 12 may vary due to different incident (and reflective) angles relative to the axis AA illustrated in FIG. For example, for purposes of the interferometric modulator 12 shown in the FIG. 7, since the off-axis along an optical path (off-axis path) propagation A _1, a first angle of the light incident on the interferometric modulator, The self-interfering modulator reflects and propagates to an observer. When the light reaches the viewer as a result of optical interference between the pair of mirrors in the interferometric modulator 12, the observer perceives the first color. When the observer moves or changes his/her position to change the viewing angle, the light received by the observer propagates along a different off-axis path A ₂ corresponding to a second incident (and reflective) angle different from the first angle. . The optical interference in the interferometric modulator 12 depends on the optical path length d of the light propagating within the modulator. Thus, different optical paths of different optical path lengths A ₁ and A ₂ from the interferometric modulator 12 outputs different outputs. As the viewing angle increases, the effective optical path of the interferometric modulator decreases according to the relationship 2d cosβ=Nλ, where β is the viewing angle (the angle between the normal of the display and the incident light). As the viewing angle increases, the peak resonant wavelength of the reflected light decreases. Therefore, the user perceives different colors depending on his or her observation angle. As described above, this phenomenon is called "color shift". The color shift is typically identified based on a color produced by the interferometric modulator 12 as viewed by the viewer along the axis AA.

Another consideration in the design of a display incorporating the interferometric modulator 12 It is the production of white light. "White" light usually refers to light that is perceived by the human eye and does not include special colors, that is, white light has nothing to do with hue. Black refers to lack of color (or light), while white refers to light that includes such a wide spectral range that no special color is perceived. White light can refer to light having a broad spectral range of visible light having a nearly uniform intensity. However, since the human eye is sensitive to the wavelengths of particular red, green, and blue light, white can be generated by mixing the intensity of the colored light to produce light having one or more spectral peaks that are perceived by the eye as "white." In addition, the color gamut of a display is the range of colors that the device can reproduce, for example, by mixing red, green, and blue light.

A white point is a display that is considered to be a large system neutral (gray or colorless) hue. The characteristics of the white point of a display device can be based on a comparison between white light produced by the device and one of the spectral content of light emitted by a black body at a particular temperature ("blackbody radiation"). A standard black system - an idealized object that absorbs all light incident on an object and re-emits the light, wherein the spectrum of the light depends on the temperature of the black body. For example, a blackbody spectrum at 6,500 °K can be referred to as white light with a color temperature of 6,500 °K. Color temperatures or white spots of approximately 5,000°-10,000°K are generally recognized as daylight.

The International Lighting Association (CIE) has published a standardized white point for light sources. For example, a light source labeled "D" refers to daylight. In particular, the standard white points D ₅₅ , D ₆₅ and D ₇₅ associated with color temperatures of 5,500 ° K, 6,500 ° K and 7,500 ° K are standard daylight white points.

A display device can be characterized by a white point of white light produced by a display. Because of the light from other sources, the human perception of the display is determined, at least in part, by the perception of white light from the display. For example, a display or light source with a lower white point (eg, D55) can be perceived by the viewer as having a yellow tint. A display with a higher temperature white point (e.g., D75) can be perceived by a user as having a "cooler" or bluer tone. Users are often more likely to react to displays with higher temperature white points. Thus, controlling the white point of a display desirably provides some control over the viewer's response to the display. Embodiments of the interferometric modulator array 30 can be configured to produce white light whose white point is selected to conform to a standard white point under one or more desired illumination conditions.

White light may be generated by pixel array 30 by having each pixel include one or more interferometric modulators 12. For example, in one embodiment, pixel array 30 includes pixels having a population of red, green, and blue interferometric modulators 12. As discussed above, by using the relationship d= N λ selects the optical path length d to select the color of the interferometric modulator 12. Moreover, the balance or relative proportion of colors produced by each pixel in pixel array 30 may be further affected by the relative reflection regions of each interferometric modulator 12 (eg, red, green, and blue interferometric modulators 12). Impact. Additionally, since the modulator 12 selectively reflects incident light, the white point of the light reflected from the pixel array 30 of the interferometric modulator 12 is typically dependent on the spectral characteristics of the incident light. In an embodiment, the white point of the reflected light can be configured to be different from the white point of the incident light. For example, in an embodiment, pixel array 30 may be configured to reflect D75 light when used in D65 daylight.

In one embodiment, the distance d and the region of the interferometric modulator 12 in the pixel array 30 are selected such that the white light produced by the pixel array 30 corresponds to a particular normalized white point under an expected illumination condition. For example, the light is emitted in the sunlight, under the fluorescent light or after forming a position to illuminate the pixel array 30. For example, the white point of pixel array 30 can be selected to be D ₅₅ , D _{65 ,} or D ₇₅ under certain lighting conditions. Moreover, the light reflected by pixel array 30 can have a different white point than the light of an intended or configured source. For example, a particular pixel array 30 can be configured to reflect D75 light when viewed in D65 sunlight. More generally, the white point of a display can be selected based on an illumination source (eg, front light) configured with the display or according to a particular viewing condition. For example, a display can be configured to have a selected white point (eg, D55, D65, or D75) when viewed under an expected or typical illumination source such as an incandescent, fluorescent, or natural light source. More specifically, for example, a display for use with a handheld device can be configured to have a selected white point when viewed under sunlight. Alternatively, a display for use in an office environment can be configured to have a selected white point (e.g., D75) when illuminated by a typical office fluorescent lamp.

Table 1 illustrates the optical path length of an embodiment. In particular, Table 1 illustrates red, green, and blue interference in two exemplary embodiments of pixel array 30 that produces D ₆₅ and D ₇₅ white light by using modulators 12 having substantially equal reflective regions. Air gap of the modulator. Table 1 assumes a dielectric layer comprising two layers (100 nm of Al ₂ O ₃ and 400 nm of SiO ₂ ). Table 1 also assumes that each of the red, green, and blue interferometric modulators 12 has substantially equal reflective areas. One of ordinary skill in the art will appreciate that a range of equivalent air gap distances can be obtained by varying the thickness or refractive index of the dielectric layer.

It should be appreciated that in other embodiments, different distances d and regions of the modulator 12 may be selected to produce other normalized white points that are set for different viewing environments. In addition, the red, green, and blue modulators 12 can also be controlled to be in a reflective or non-reflective state for different amounts of time to further change the relative balance of reflected red, green, and blue light, thereby changing the white point of the reflected light. . In an embodiment, the ratio of the reflective regions of each color modulator 12 can be selected to control white points in different viewing environments. In an embodiment, the optical path length d may be selected such that it corresponds to a common multiple of one or more visible resonant wavelengths (eg, first, second, or third peaks of red, green, and blue) to The interferometric modulator 12 reflects white light characterized by three of its spectral effects. In this embodiment, the optical path length d is selected such that the resulting white light corresponds to a normalized white point.

In addition to the group of red, green, and blue interferometric modulators 12 in pixel array 30, other embodiments include other methods of producing white light. For example, one embodiment of pixel array 30 includes cyan and yellow interferometric modulators 12, i.e., interferometric modulators 12 having respective pitches d to produce cyan and yellow light. The mixed spectral response of the cyan and yellow interferometric modulators 12 produces light having a broad spectral response that is perceived as "white." The cyan and yellow modulators are positioned closely to allow an observer to perceive such a mixed response. For example, in one embodiment, the cyan variator and the yellow modulator are arranged in adjacent columns of the pixel array 30. In another embodiment, the cyan variator and the yellow modulator are arranged in adjacent rows of the pixel array 30.

FIG. 8 is a diagram illustrating the spectral response of an embodiment including cyan and yellow interferometric modulators 12 to produce white light. The horizontal axis represents the wavelength of the reflected light. The vertical axis represents the relative reflectance of the light incident on the modulator 12. Trace 80 illustrates the response of the cyan variator, which is a single peak that focuses on the cyan portion of the spectrum between, for example, blue and green. Trace 82 illustrates the response of the yellow modulator, which is a single peak that focuses on the yellow portion of the spectrum between, for example, red and green. Trace 84 illustrates the mixed spectral response of a pair of cyan and yellow modulators 12. Although trace 84 has two peaks at the cyan and yellow wavelengths, it is sufficiently equal in the visible spectrum to cause the light reflected from modulator 12 to be perceived as white.

In one embodiment, pixel array 30 includes a first level yellow interferometric modulator and a second level cyan interferometric modulator. When the pixel array 30 is viewed from an increasing off-axis angle, the light reflected by the first stage yellow modulator is shifted toward the blue end of the spectrum, for example, the modulator at an angle has an effective d, which is equal to d of the first level cyan. At the same time, the light reflected by the second level cyan variator is offset to correspond to the light from the first level yellow modulator. Thus, as the correlation peak shifts the spectrum, the total mixed spectral response is broad and relatively balanced across the visible spectrum. The pixel array 30 thus produces white light over a relatively large range of viewing angles.

In one embodiment, a display having cyan and yellow modulators can be configured to produce white light having a selected normalized white point under one or more viewing conditions. For example, the spectral response of the cyan variator and the yellow modulator can be selected under selected lighting conditions including D55, D65, or D75 light, such as sunlight for displays suitable for outdoor use, such that the reflected light has One is the white point of D55, D65, D75 or any other suitable white point. In an embodiment, the modulator can be configured to reflect light having a different white point than incident light from a desired or selected viewing condition.

9 is a side cross-sectional view of an interferometric modulator 12 having a layer of material 102 for selectively transmitting light of a particular color. In an exemplary embodiment, layer 102 is on the side of substrate 20 opposite modulator 12. In one embodiment, the material layer 102 includes a magenta filter in which the green interferometric modulator 12 is viewed through a magenta filter. In an embodiment, material layer 102 is a dyed material. In one such embodiment, the material is a dyed photoresist material. In an embodiment, the green interferometric modulator 12 is a first stage green interferometric modulator. Filter layer 102 is configured to transmit magenta light when illuminated by a substantially uniform white light. In an exemplary embodiment, light is incident on layer 20 and filtered light is transmitted from layer 20 to modulator 12. The modulator 12 reflects the filtered light back through the layer 102. In this embodiment, light passes through layer 102 twice. In this embodiment, the thickness of material layer 102 can be selected to compensate for and utilize this dual filtration. In another embodiment, a front light structure can be positioned between layer 102 and modulator 12. In this embodiment, the material layer 102 only acts on the light reflected by the modulator 12. In these embodiments, layer 102 is selected accordingly.

FIG. 10 is a diagram illustrating the spectral response of an embodiment including a green interferometric modulator 12 and a "magenta" filter layer 102. The horizontal axis represents the wavelength of the reflected light. The vertical axis represents the relative spectral response of light incident on green modulator 12 and filter layer 102 to the visible spectrum. Trace 110 illustrates the response of green modulator 12, which is a single peak that is concentrated in the green portion of the spectrum (e.g., near the center of the visible spectrum). Trace 112 illustrates the response of the magenta filter formed by material layer 102. Trace 112 has two relatively flat portions on either side of the lowest u-shaped portion of the center. Trace 112 thus represents the response of a magenta filter that selectively transmits substantially all of the red and blue light while filtering out light in the green portion of the spectrum. Trace 114 illustrates the mixed spectral response of the green modulator 12 paired with the filter layer 102. Trace 114 illustrates the filtering of light due to filter layer 102, the spectral response of which is at a level of reflection that is lower than the spectral response of green modulator 12. However, the spectral response is relatively equal in the visible spectrum such that the light filtered from the green modulator 12 and the magenta filter layer 102 is perceived as white.

In one embodiment, a display having a green modulator 12 and a magenta filter layer 102 can be configured to produce white light having a selected normalized white point under one or more viewing conditions. For example, the spectral response of the green modulator 12 and the spectrum of the magenta filter layer 102 can be selected under selected lighting conditions including D55, D65, or D75 light, such as sunlight for displays suitable for outdoor use. The response is such that the reflected light has a white point of D55, D65, D75, or any other suitable white point. In an embodiment, the modulator can be configured to reflect light having a different white point than incident light from a desired or selected viewing condition.

11A and 11B are system block diagrams illustrating an embodiment of a display device 2040. Display device 2040 can be, for example, a cellular phone or a mobile phone. However, the same components of display device 2040 or slight variations thereof may also illustrate various types of display devices, such as televisions or portable media players.

The display device 2040 includes a housing 2041, a display 2030, an antenna 2043, a speaker 2045, an input device 2048, and a microphone 2046. Housing 2041 is typically fabricated from any of a variety of manufacturing processes well known to those skilled in the art, including injection molding and vacuum forming. Additionally, the outer casing 2041 can be made from any of a variety of materials including, but not limited to, plastic, metal, glass, rubber, and ceramic, or combinations thereof. In an embodiment, the housing 2041 includes a removable portion (not shown) that is interchangeable with other removable portions having different colors or containing different logos, pictures, or symbols.

Display 2030 of exemplary display device 2040 can be any of a variety of displays, including bi-stable displays as described herein. In other embodiments, display 2030 includes a flat panel display, such as a plasma, EL, OLED, STN LCD, or TFT LCD as described above, or a non-flat panel display, such as a CRT, as is well known to those skilled in the art. Or other tubular devices. However, as described herein, for purposes of describing the present embodiment, display 2030 includes an interferometric modulator display.

The components of one embodiment of an exemplary display device 2040 are schematically illustrated in FIG. 11B. The illustrated exemplary display device 2040 includes a housing 2041 and can include additional components that are at least partially enclosed within the housing 2041. For example, in an embodiment, the exemplary display device 2040 includes a network interface 2027. The network interface 2027 includes an antenna 2043 coupled to a transceiver 2047. The transceiver 2047 is coupled to the processor 2021 coupled to the conditioning hardware 2052. The conditioning hardware 2052 can be configured to adjust a signal (eg, to filter the signal). The adjustment hardware 2052 is connected to a speaker 2045 and a microphone 2046. The processor 2021 is also coupled to an input device 2048 and a driver controller 2029. The driver controller 2029 is coupled to a frame buffer 2028 and an array driver 2022. The array driver 2022 is coupled to a display array 2030. A power source 2050 supplies power to all components in accordance with the design requirements of the particular exemplary display device 2040.

The network interface 2027 includes an antenna 2043 and a transceiver 2047 such that the illustrative display device 2040 can communicate with one or more devices over a network. In an embodiment, the network interface 2027 may also have some processing power to reduce the requirements on the processor 2021. Antenna 2043 is any antenna known to those skilled in the art for transmitting and receiving signals. In an embodiment, the antenna transmits and receives RF signals in accordance with the IEEE 802.11 standard, including IEEE 802.11 (a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals in accordance with the BLUETOOTH standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS or other conventional signals for communicating within a wireless cellular telephone network. The transceiver 2047 preprocesses the signals received from the antenna 2043 such that the signals can be received by the processor 2021 and further processed. Transceiver 2047 also processes the signals received from processor 2021 such that it can be transmitted from exemplary display device 2040 via antenna 2043.

In an alternate embodiment, transceiver 2047 can be replaced by a receiver. In another alternative embodiment, the network interface 2027 can be replaced by an image source that can store or generate image data to be sent to the processor 2021. For example, the image source can be a digital video disc (DVD) or a hard disk drive containing image data or a software module for generating image data.

Processor 2021 typically controls the overall operation of exemplary display device 2040. The processor 2021 receives data from the network interface 2027 or an image source, such as compressed image data, and processes the data into raw image data or a format that is easily processed into the original image data. Thereafter, the processor 2021 sends the processed data to the drive controller 2029 or the frame buffer 2028 for storage. Raw material generally refers to information that identifies image features at each location within an image. For example, the image features may include color, saturation, and gray-scale levels.

In one embodiment, processor 2021 includes a microprocessor, CPU, or logic unit for controlling the operation of exemplary display device 2040. The conditioning hardware 2052 typically includes an amplifier and filter for transmitting signals to and receiving signals from the speaker 2045. The conditioning hardware 2052 can be a decentralized component within the exemplary display device 2040 or can be included within the processor 2021 or other components.

The driver controller 2029 obtains the raw image data generated by the processor 2021 directly from the processor 2021 or from the frame buffer 2028 and reformats the original image material appropriately for high speed transmission to the array driver 2022. In particular, the driver controller 2029 reformats the raw image data into a data stream having a raster-like format such that it has a time sequence suitable for scanning the entire display array 2030. Thereafter, the driver controller 2029 sends the formatted information to the array driver 2022. Although a driver controller 2029 (e.g., an LCD controller) is typically associated with system processor 2021 as a separate integrated circuit (IC), the controllers can be implemented in a variety of ways. It can be embedded in the processor 2021 as a hardware, embedded in the processor 2021 as a software, or fully integrated with the array driver 2022 in a hardware form.

Typically, array driver 2022 receives the formatted information from driver controller 2029 and reformats the video data into a set of parallel waveforms that are applied multiple times per second to the X-y pixel matrix from the display. Hundreds and sometimes thousands of wires.

In an embodiment, driver controller 2029, array driver 2022, and display array 2030 are suitable for use with any type of display described herein. For example, in one embodiment, the driver controller 2029 is a conventional display controller or a bi-stable display controller (eg, an interferometric modulator controller). In another embodiment, array driver 2022 is a conventional driver or a bi-stable display driver (eg, an interferometric modulator display). In one embodiment, a driver controller 2029 is integrated with the array driver 2022. This embodiment is common in highly integrated systems such as cellular phones, watches, and other small area displays. In yet another embodiment, display array 2030 is a typical display array or a bi-stable display array (eg, a display including an array of interferometric modulators).

Input device 2048 allows a user to control the operation of exemplary display device 2040. In one embodiment, the input device 2048 includes a keypad (eg, a QWERTY keyboard or a telephone keypad), a button, a switch, a touch sensitive screen, a pressure sensitive or temperature sensitive film. In an embodiment, the microphone 2046 is an input device of the illustrative display device 2040. When data is input to the device using the microphone 2046, the user can provide voice commands to control the operation of the exemplary display device 2040.

Power source 2050 can include a variety of energy storage devices that are well known in the art. For example, in one embodiment, the power source 2050 is a rechargeable battery, such as a nickel-cadmium battery or a lithium ion battery. In another embodiment, the power source 2050 is a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell and a solar-cell paint. In another embodiment, the power source 2050 is configured to receive power from a wall outlet.

As noted above, in some embodiments, control programmability resides in a drive controller that can be located in several locations in the electronic display system. In some cases, control programmability exists in array driver 2022. Those skilled in the art will appreciate that the above optimizations can be implemented in any number of hardware and/or software components and in a variety of configurations.

While the above Detailed Description of the Invention has been shown and described, it is intended to be illustrative of the embodiments of the present invention. Various omissions, substitutions, and alterations are made in the form and details of the process. It will be appreciated that the invention may be embodied in a form that does not provide all of the features and advantages disclosed herein. The scope of the invention should be pointed out by the appended claims rather than the description. All changes that come within the meaning and range of equivalence of the claims are intended to be included within the scope of the claims.

1, 2, 3. . . Rows and columns of pixel arrays

12, 12a, 12b. . . Interferometric modulator / pixel

14, 14a, 14b. . . Movable highly reflective layer / mirror

16, 16a, 16b. . . Fixed partial reflection layer / mirror

18. . . Column/support

19. . . Air gap / cavity

20. . . Transparent substrate

21, 2021. . . processor

twenty two. . . Array controller

twenty four. . . Column driver circuit

26. . . Row driver circuit

30. . . Interferometric modulator array / pixel array

32. . . Tether

34. . . Deformable layer

80, 82, 84, 110, 112, 114. . . Trace

102. . . Magenta filter

104. . . Dielectric layer

2022. . . Array driver

2027. . . Network interface

2028. . . Frame buffer

2029. . . Drive controller

2030. . . Display array/display

2040. . . Display device

2041. . . shell

2043. . . antenna

2045. . . speaker

2046. . . microphone

2047. . . transceiver

2048. . . Input device

2050. . . power supply

2052. . . Adjusting hardware

A1, A2. . . Off-axis path / optical path

AA. . . Axis

d. . . Characteristic distance / optical path length

1 is an isometric view of a portion of an embodiment of an interferometric modulator display in which one of the first interferometric modulators has a movable reflective layer in a release position and a second interferometric type The movable reflective layer of the modulator is in a triggering position.

2 is a system block diagram illustrating an embodiment of an electronic device incorporating a 3 x 3 interferometric modulator display.

3 is a graph of the position of a movable mirror and an applied voltage for an exemplary embodiment of the interferometric modulator of FIG. 1.

4 is an illustration of one of the column voltages and row voltages that can be used to drive an interferometric modulator display.

Figure 5A illustrates an exemplary display data frame of the 3 x 3 interferometric modulator display of Figure 2.

Figure 5B illustrates an exemplary timing diagram that can be used to write the frame of Figure 5A to a column signal and a row signal.

Figure 6A is a cross-sectional view of the apparatus of Figure 1.

Figure 6B is a cross-sectional view of an alternate embodiment of an interferometric modulator.

Figure 6C is a cross-sectional view of another alternate embodiment of an interferometric modulator.

Figure 7 is a side cross-sectional view of the interferometric modulator illustrating the optical path through the modulator.

Figure 8 is a diagram illustrating the spectral response of an embodiment comprising cyan and yellow interferometric modulators to produce white light.

Figure 9 is a side cross-sectional view of the interferometric modulator having a layer of material for selectively transmitting light of a particular color.

Figure 10 is a diagram illustrating the spectral response of an embodiment comprising a green interferometric modulator and a "magenta" color filter layer to produce white light.

11A and 11B are system block diagrams illustrating one embodiment of a visual display device including a plurality of interferometric modulators.

12. . . Interferometric modulator / pixel

20. . . Transparent substrate

AA. . . Axis

A1, A2. . . Off-axis path / optical path

Claims (65)

A display device comprising: a plurality of interferometric modulators, the plurality of interferometric modulators comprising: at least one interferometric modulator configured to output red light; configured to output green light At least one interferometric modulator; and at least one interferometric modulator configured to output blue light, wherein the apparatus is configured such that when illuminated with light having a different white point, the red light, the green Light and the blue light are mixed to produce white light having a normalized white point, and wherein the apparatus is configured to adjust the plurality of interferometric modulators to control the white point of the generated white light for different viewing environments. The apparatus of claim 1, wherein each of the plurality of interferometric modulators comprises a reflective area, and wherein the respective areas are selected to produce the white light having the normalized white point. The apparatus of claim 1, wherein the normalized white point is one of standard white points D55, D65 or D75, which are associated with color temperatures of 5500°K, 6500°K, and 7500°K, respectively. The apparatus of claim 1, further comprising an illumination source for the plurality of interferometric modulators, the illumination source having a different white point than the white light having the normalized white point produced . The device of claim 1, wherein each of the plurality of interferometric modulators comprises a reflective region, and wherein the device is configured to adjust for outputting the red light, the green light, and the blue light based on observation The environment controls a ratio of one of the reflective regions of the white point of the generated white light. The device of claim 1, wherein the device is configured to output the red light, the green light, and the blue light by the interferometric modulator to control the white point of the generated white light based on an observation environment , adjust the amount of time. The device of claim 1, wherein the different viewing environments comprise an office environment and a sunlight environment. A display device comprising: a plurality of display elements, each of the display elements comprising an interferometric modulator having a reflective surface configured to be moved and positioned at a distance from a portion of the reflective surface Where the plurality of display elements are configured to produce white light characterized by a normalized white point when illuminated with white light having different white points, and wherein the plurality of display elements are configured to be adjustable for control The white point of the generated white light in different viewing environments. The device of claim 8, wherein the plurality of display elements comprise a plurality of display elements having different spectral outputs that together produce the white light characterized by the normalized white point. The device of claim 8, wherein the plurality of display elements comprise a plurality of display elements having a region from which light is reflected, and wherein the respective regions of the display elements are selected to produce a characteristic white point The white light. The device of claim 8, wherein the plurality of display elements comprise at least one display element configured to output red light, at least one display element configured to output green light, and at least one display element configured to output blue light. The device of claim 8, wherein the plurality of display elements comprise configured One or more display elements of the white light are individually output. The device of claim 8, wherein the reflective surface is positioned at a distance from the partially reflective surface to produce the white light characterized by the normalized white point. The apparatus of claim 8, wherein the normalized white point is one of standard white points D55, D65 or D75, which are associated with color temperatures of 5500°K, 6500°K, and 7500°K, respectively. The device of claim 8, further comprising at least one filter associated with the at least one display element, the filter configured to selectively transmit certain visible wavelengths and filter other visible when illuminated with white light wavelength. The apparatus of claim 8 further comprising an illumination source for the plurality of display elements, the illumination source having a different white point than the normalized white point. The device of claim 8 further comprising: a processor in electrical communication with the plurality of display elements, the processor configured to process the image material; and a memory device in electrical communication with the processor. The apparatus of claim 17, further comprising a driver circuit configured to transmit the plurality of signals to the plurality of display elements. The apparatus of claim 18, further comprising a controller configured to send at least a portion of the image data to the driver circuit. The device of claim 17, further comprising an image source module configured to send the image data to the processor. The device of claim 20, wherein the image source module comprises at least one of a receiver, a transceiver, and a transmitter. The device of claim 17, further comprising an input device configured to receive input data and to communicate the input data to the processor. The apparatus of claim 8, wherein each of the plurality of display elements comprises a reflective area, and wherein a ratio of one of the reflective areas for outputting different colored lights is adjustable to control the generated white light based on an observation environment The white point. The apparatus of claim 8 wherein the different amounts of light are modulated by the display elements, the respective amounts of time being adjustable to control the white point of the generated white light based on the viewing environment. The device of claim 8, wherein the different viewing environments comprise an office environment and a sunny environment. A method of fabricating a display, comprising: forming each of a plurality of display elements having an interferometric modulator configured to output light, wherein forming the display elements comprises forming a portion of a reflective surface and configured Reflecting surface moved and positioned at a distance from the partially reflective surface, wherein the plurality of display elements are formed such that when illuminated with white light having a different white point, the display elements are produced with a normalized white point Characterized white light, and wherein the display is configured to adjust the display elements to control the white point of the generated white light for different viewing environments. The method of claim 26, wherein the display elements are formed to have a self Each of the regions of reflected light and having respective distances, the respective regions and the respective distances are selected such that the at least two display elements produce the white light characterized by the normalized white point. The method of claim 26, wherein forming the plurality of display elements comprises forming at least one display element configured to output red light, at least one display element configured to output green light, and configured to output at least blue light A display element. The method of claim 26, wherein forming the plurality of display elements comprises forming at least one display element configured to output white light individually. The method of claim 26, further comprising providing at least one filter associated with the at least one display element, the at least one filter configured to selectively transmit certain visible wavelengths and filter out other visible wavelengths . The method of claim 26, wherein the white point is one of standard white points D55, D65 or D75, which are associated with color temperatures of 5500°K, 6500°K, and 7500°K, respectively. The method of claim 26, wherein each of the display elements comprises a reflective area, and wherein the display is configured to adjust a ratio of the ones of the reflective areas for reflecting different colored lights to control the The white point of the white light produced. The method of claim 26, wherein the display is configured to adjust the respective amount of time when the different color lights are reflected by the display element to control the white point of the generated white light based on the viewing environment. The method of claim 26, wherein the different viewing environments comprise an office environment and a sunny environment. A display made by the method of claim 26. A display device comprising: a first member for selectively reflecting light having a first color; a second member for selectively reflecting light having a second color; for selectively reflecting having a third member of light of a third color; and means for adjusting the first, second, and third light reflecting members, wherein the first, second, and third light reflecting members are included Separatingly interfering with the first member, the second member, and the third member of the modulated light, wherein the display device is configured such that when illuminated with white light having a different white point, the first, the second, and the first The reflected light of the three light reflecting members is mixed to produce white light characterized by a normalized white point, and wherein the means for adjusting is configured to adjust the first, second and third light reflecting members to control The white point of the generated white light for different viewing environments. The apparatus of claim 36, wherein the first, second and third light reflecting members for selectively reflecting light comprise a plurality of display elements, each of the display elements comprising a configuration configured to be moved And a reflective surface positioned at a distance from a portion of the reflective surface. The device of claim 36, further comprising means for selectively transmitting certain visible wavelengths and filtering out other visible wavelengths. The device of claim 38, wherein the selectively transmissive member comprises a filter. The device of claim 36, wherein the normalized white point is a standard white point D55, One of D65 or D75, which is associated with color temperatures of 5500°K, 6500°K, and 7500°K, respectively. The device of claim 36, further comprising an illumination member having the different white color as compared to the white light generated by the first, second, and third light reflecting members for selectively reflecting light point. The device of claim 36, wherein the first and second light reflecting members for selectively reflecting light comprise first and second pixels, respectively. The apparatus of any one of claims 36-42, wherein the first, second, and third light reflecting members for selectively reflecting light comprise first, second, and third interferometric modulators, respectively . The apparatus of claim 36, wherein each of the first, second and third light reflecting members comprises a reflective area, and wherein the means for adjusting is configured to adjust for reflecting the first And a ratio of one of the reflection regions of the second and third color lights to control the white point of the generated white light based on an observation environment. The apparatus of claim 36, wherein the first, second, and third light reflecting members control the white point of the generated white light based on an observation environment, the means for adjusting is configured to adjust each The amount of time. The device of claim 36, wherein the different viewing environments comprise an office environment and a sunny environment. A display device comprising: a member for displaying an image, comprising a member for interferometric modulated light, the member for interferometric modulated light comprising: a member for reflecting light; a member for partially reflecting light, and a member for adjusting the member for reflecting light and the member for partially reflecting light, wherein the display member is configured when illuminated with white light having a different white point Outputting white light characterized by a normalized white point, and wherein the means for adjusting is configured to adjust the member for reflecting light and the member for partially reflecting light to control for different viewing environments The white point of the output white light. The device of claim 47, wherein the partially reflective member comprises a portion of the reflective surface and the reflective member comprises a reflective surface. The device of claim 47, wherein the display member comprises at least one display element. The apparatus of claim 49, wherein the at least one display element comprises a plurality of display elements having different spectral outputs, the plurality of display elements together producing the white light characterized by the normalized white point. The apparatus of claim 49, wherein the at least one display element comprises at least one display element configured to output red light, a display element configured to output green light, and a display element configured to output blue light, wherein the red Light, the green light, and the blue light are mixed to produce the output white light. The device of claim 49, wherein the at least one display element comprises each of a plurality of display elements having a region from which light is reflected, and wherein the respective regions of the display elements are selected to be produced by the standardization The white point is characterized by white light. The device of claim 49, wherein the at least one display element comprises a group The state outputs one or more display elements of white light individually. The apparatus of claim 49, wherein the at least one display element comprises one or more display elements configured to individually output the white light characterized by the normalized white point. The device of claim 49, wherein the reflective surface is configured to be moved and positioned at a distance from the partially reflective surface to produce the white light characterized by the normalized white point. The device of claim 49, wherein the at least one display element comprises a filter configured to selectively transmit certain visible wavelengths and filter out other visible wavelengths. The apparatus of claim 47, wherein the normalized white point is one of standard white points D55, D65 or D75, which are associated with color temperatures of 5500°K, 6500°K, and 7500°K, respectively. The device of claim 47, further comprising means for filtering, the filter member configured to selectively transmit certain visible wavelengths and filter out other visible wavelengths when illuminated with white light. The device of claim 58, wherein the filter member comprises at least one filter. The device of claim 47, further comprising means for illuminating the reflective member and the partially reflective member, the illumination member outputting light having the white point different from the normalized white point. The device of claim 60, wherein the illumination member comprises an illumination source. The device of claim 47, wherein the display member comprises at least one interferometric modulator. The device of claim 47, wherein the means for reflecting light and the means for partially reflecting light comprise an area from which light is reflected, and wherein the means for adjusting is configured A ratio of one of the individual regions for reflecting different colored lights is adjusted to control the white point of the output white light based on the viewing environment. The apparatus of claim 47, wherein the member for adjusting is configured to control the white point of the output white light based on the observation environment by the member for reflecting light and the member for partially reflecting light reflecting different color lights It is configured to adjust individual amounts of time. The device of claim 47, wherein the different viewing environment comprises an office environment and a sunlight environment.